What does it mean when my cat walks around meowing for 20 minutes straight (on several occasions)?

Mine do that too sometimes. I think they may be hearing another cat outside and are possibly talking to it. They also see things that we humans do not and they may be talking to that too.

Sometimes I just think they are doing it to hear themselves meow.

I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.